JP2010133002A - Method for removing copper contained in steel scraps - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently removing copper contained in steel scraps without needing a large-scaled facility, when a high-grade steel is produced by using the copper-containing steel scraps as an iron source. <P>SOLUTION: The method for removing the copper contained in the steel scraps, is performed as the followings that the copper-containing steel scrap is carburize-melted to produce molten iron for steel-making, and thereafter, the copper contained in this molten iron is removed by using sulfur-containing flux, and successively, the sulfur contained in the molten iron is removed. In this case, as the sulfur-containing flux, it is preferable to use the flux mainly containing Na<SB>2</SB>S, and it is preferable that the removal-treatment of the copper contained in the molten iron is performed with a mechanical-stirring type refining equipment or with a flux injection method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for removing copper in steel scrap, which causes quality problems when high-grade steel is produced using steel scrap (iron-based scrap) as an iron source.

The iron source used in the steelmaking process is mainly hot metal obtained by reducing iron ore in a blast furnace, but with the aging of steel scraps, buildings and machinery products generated in the processing process of steel materials A considerable amount of steel scrap is also used. The production of hot metal in the blast furnace requires a great deal of energy to reduce and melt iron ore, whereas steel scrap requires only heat of melting, and when steel scrap is used in the steelmaking process, There is an advantage that the amount of energy used for reducing heat of iron ore can be reduced. Therefore, from the viewpoint of energy saving and prevention of global warming by reducing CO _2, it is desired to promote the use of steel scrap.

  Conventionally, steel scrap is often used by directly feeding it into a steelmaking furnace such as a converter or an electric furnace. However, when various steel scraps are used as the iron source, there is a problem that it is difficult to adjust the composition of the molten steel to be produced. Moreover, since the converter uses the combustion heat of carbon in the hot metal as the melting heat of steel scrap, there is a disadvantage that the mixing ratio of steel scrap cannot be increased, while the electric furnace has low energy efficiency. There was a drawback in terms of energy consumption. Therefore, in recent years, a method of using a vertical furnace with high energy efficiency, melting steel scraps by a simple and low-cost method in the pre-process of the converter, and making the composition as uniform as possible has attracted attention.

By the way, when recycling steel scraps, trump elements represented by copper and tin accompanying these steel scraps are inevitably mixed in the molten iron in the process of steel scrap melting. The trump element is a component that impairs the properties of steel and must be kept below a certain concentration. For this reason, it has been difficult to use low-grade steel scrap that may contain copper or tin as an iron source for producing high-grade steel. However, considering the recent increase in steel scrap generation and the demand for increased use of steel scrap to reduce CO ₂ generation, it is necessary to promote recycling of lower steel scrap.

  As a practical technology for using the current low-grade steel scrap, the steel scrap is physically decomposed, the harmful parts are separated by methods such as human power and magnetic separation, and the harmful parts are separated. There is no effective method other than blending with raw materials containing almost no components and using them within the range where there is no problem in the material properties of the steel. With such a method, it is impossible to recycle a large amount of scrap steel from used cars, etc., and it is sufficient as a technology for removing copper in steel scrap corresponding to the era of the large amount of scrap scrap expected in the future. Cannot be a good solution.

On the other hand, the principle invention described below is known about the copper removal method after mixing in molten iron. That is, the basic technical knowledge of contacting the copper-containing high carbon molten iron with the FeS-Na ₂ S-based flux and separating and removing the copper component in the molten iron as Cu ₂ S is disclosed in Non-Patent Document 1 and Non-Patent Document. 2 is reported. This technique proposes a wider applicability to the above-described physical removal method as a copper removal technique. However, this method has a problem that a sulfur (S) component is mixed into the molten iron from the Na ₂ S-based flux. Moreover, the distribution ratio, which is the ratio of the Cu concentration in the slag formed on the molten iron by melting the flux and the Cu concentration in the molten iron, is about 30 at most, and the distribution ratio is lowered by giving sufficient stirring to the slag. It is necessary not to let it.

As a decoppering treatment method based on this fundamental technical knowledge, Patent Document 1 discloses that a copper-containing high-carbon molten iron is obtained by carburizing and melting copper-containing steel scrap, and then contacting with a flux mainly composed of Na ₂ S. A method is disclosed in which the copper component in molten iron is separated and removed in the Na ₂ S flux as Cu ₂ S by reacting.

  However, Patent Document 1 does not disclose any desulfurization of high carbon molten iron after copper removal. Moreover, although the copper removal treatment is performed by stirring the hot metal and slag by blowing Ar gas from the bottom of the reaction vessel (hot metal ladle), stirring of the slag is insufficient. In order to compensate for this, an electric heating device for maintaining a reaction temperature of 1200 to 1500 ° C. is provided, and a covered reaction vessel for cutting off contact with the atmosphere is used, but the equipment is large-scale, It has not been established as a practical technology.

Japanese Patent Laid-Open No. 4-198431

Masato Imai, iron and steel, vol.74 (1988) No.4. p. 640 Oshio et al., Iron and Steel, vol.77 (1991) No.4. p. 504

  The present invention has been made in view of the above circumstances, and the object of the present invention is to efficiently and large-scale copper in steel scrap when manufacturing high-grade steel using copper-containing steel scrap as an iron source. It is to provide a method for removing equipment without the need for it.

  The method for removing copper in steel scraps according to the first aspect of the present invention for solving the above-mentioned problem is to produce a hot metal for steel making by carburizing and melting copper-containing steel scraps, and then sulfur contained in the hot metal It removes using a containing flux, Then, the sulfur contained in a hot metal is removed, It is characterized by the above-mentioned.

The method for removing copper in scraps according to the second invention is characterized in that, in the first invention, the sulfur-containing flux contains Na ₂ S as a main component.

According to a third aspect of the present invention, there is provided a method for removing copper in steel scraps according to the first or second aspect of the present invention, wherein a starting material for the sulfur-containing flux is a material mainly composed of Na ₂ CO ₃ and an iron-sulfur alloy. It is characterized by being used.

  The method for removing copper in steel scrap according to the fourth aspect of the present invention is the hot metal before removing copper by the sulfur-containing flux in any of the first to third aspects, wherein the temperature is 1200 ° C. or higher and 1500 ° C. or lower. The carbon concentration is 2% by mass or more and the copper concentration is 0.1% by mass or more and 1.0% by mass or less.

  The method for removing copper in steel scrap according to the fifth invention is characterized in that, in the fourth invention, the hot metal before removing copper by the sulfur-containing flux has a temperature of 1250 ° C. or higher and 1350 ° C. or lower. To do.

  The method for removing copper in steel scraps according to a sixth aspect of the present invention is the hot metal before removing copper by the sulfur-containing flux in any one of the first to fifth aspects, wherein the sulfur concentration is 0.01% by mass. It is the above, It is characterized by the above.

  The method for removing copper in steel scraps according to a seventh aspect of the present invention is characterized in that, in any one of the first to sixth aspects, the copper contained in the molten iron is removed by a mechanical stirring type refining apparatus. Is.

  According to an eighth aspect of the present invention, there is provided a method for removing copper in steel scraps according to any one of the first to sixth aspects, wherein the copper contained in the molten iron is removed in a reaction vessel together with a sulfur-containing flux along with a carrier gas. It is characterized by being blown into the hot metal.

  According to a ninth aspect of the present invention, there is provided a method for removing copper in steel scraps according to any one of the first to eighth aspects, wherein the copper-containing steel scraps are added using a vertical furnace in which a carbon material bed is formed. It is characterized by melting charcoal.

  According to a tenth aspect of the present invention, there is provided a method for removing copper in steel scraps according to any one of the first to sixth aspects, wherein the copper-containing steel scraps are added using a vertical furnace in which a carbon material bed is formed. The sulfur-containing flux is supplied to the hot metal flowing through the cast iron from the vertical furnace to the hot metal holding container, and the copper in the hot metal is removed.

  The method for removing copper in steel scraps according to an eleventh aspect of the invention is characterized in that, in any one of the first to tenth aspects, a removal process of sulfur contained in the hot metal is performed with a mechanical stirring type refining apparatus. Is.

  A method for removing copper in steel scraps according to a twelfth aspect of the present invention is the method for removing copper in the first to eleventh aspects, wherein the blast furnace hot metal is mixed with the hot metal after the copper is removed by the sulfur-containing flux, and then the blast furnace It is characterized by removing sulfur contained in the hot metal mixed with hot metal.

  According to the present invention, after the copper-containing steel scrap is carburized and melted, the copper in the hot metal brought from the steel scrap is separated and removed into the sulfur-containing flux. Copper that was difficult to separate by separation and removal methods such as sorting can be separated efficiently, and after the copper removal treatment, the sulfur removal treatment brought from the sulfur-containing flux is performed. The hot metal containing less copper and sulfur can be efficiently obtained from the copper-containing steel scrap. As a result, the copper-containing steel scrap can be used as an iron source for high-grade steel, and the use of lower-grade steel scrap is promoted.

It is a figure which shows the relationship between the hot metal temperature before a copper removal process, and a copper removal rate.

  The present invention will be specifically described below.

When the hot metal for steelmaking containing carbon is produced by carburizing and dissolving copper-containing steel scrap, almost all of the copper in the steel scrap is dissolved in the hot metal. In the present invention, as a means for removing the copper, the sulfur-containing flux is brought into contact with the hot metal, and the copper in the hot metal is separated and removed as copper sulfide (Cu ₂ S) in the sulfur-containing flux. As the sulfur-containing flux, those containing an alkali metal or alkaline earth metal sulfide as a main component are suitable. In order to increase the sulfur content in the sulfur-containing flux, FeS (iron sulfide) may be mixed. Particularly suitable is a flux mainly composed of Na ₂ S. In the case of a flux mainly composed of Na ₂ S, if Na ₂ CO ₃ (soda ash) widely used industrially is used as the Na source, and an iron-sulfur alloy (ferrosulfur) is used as the sulfur source, This is advantageous in terms of cost. As the composition of the sulfur-containing flux, it is desirable that the molar fraction of Na ₂ S in the flux is 0.2 or more from the viewpoint of efficient copper removal.

  By the way, although copper removal by a sulfur-containing flux has been confirmed in principle, it is a process with a low distribution ratio (ratio between the Cu concentration in the flux and the Cu concentration in the molten iron), so the copper removal proceeds sufficiently. In order to achieve this, it is necessary to promote mass transfer on the slag side formed in the reaction vessel by adding a sulfur-containing flux. For this purpose, it is important to also stir the slag layer. In particular, in the present invention, the copper removal treatment is performed in the hot metal stage, the hot metal temperature range (1200 to 1400 ° C.) is lower than the molten steel temperature range (1550 to 1700 ° C.), and the slag fluidity is also low. Slag agitation is important.

  As a method of simultaneously stirring the molten iron and the slag present on the molten iron, the stirring slag is blown from the injection lance immersed in the molten iron in the reaction vessel or the tuyere installed at the bottom of the reaction vessel, and the slag and molten iron are stirred. Although a method can also be adopted, in the present invention, it is preferable to perform a copper removal treatment using a mechanical stirring type refining apparatus because good stirring can be obtained. As a mechanical stirring type refining apparatus, stirring using an impeller (also referred to as “stirring blade”) is typical. In other words, the impeller is immersed in the hot metal contained in a ladle-shaped reaction vessel, and the impeller is rotated about the axis of rotation to forcibly stir the hot metal and the sulfur-containing flux added on the hot metal. Is the method. In the mechanical stirring type refining apparatus, the sulfur-containing flux charged on the hot metal is sufficiently entrained in the hot metal, and the hot metal and the sulfur-containing flux are sufficiently stirred. On the other hand, in the gas stirring method disclosed in Patent Document 1, the slag is not easily caught in the hot metal, and stirring is insufficient.

  Further, a method of blowing a powdery sulfur-containing flux into the hot metal together with the conveying gas from an injection lance immersed in the hot metal, so-called flux blowing method, is also a preferable processing method. In this case, the powdered sulfur-containing flux blown into the hot metal is in direct contact with the hot metal, and new unreacted sulfur-containing flux is continuously in contact with the hot metal, facilitating mass transfer on the slag side. The effect equivalent to the case where it is made to develop is exhibited, and the reaction between the hot metal and the sulfur-containing flux is promoted. Further, since the carrier gas also functions as a stirring gas, although the stirring strength is not as high as that of the mechanical stirring type refining apparatus, the hot metal and the hot metal slag are stirred.

  In the copper removal treatment, an inert gas such as Ar gas or a reducing gas such as propane may be supplied onto the hot metal bath surface in order to prevent air from entering the atmosphere. After the copper removal treatment, the slag formed by adding the sulfur-containing flux is removed from the system.

  In the present invention, the temperature of the hot metal before copper removal treatment, that is, the temperature of the hot metal for steelmaking containing carbon produced by carburizing and melting the copper-containing steel scrap is 1200 ° C. or higher and 1500 ° C. or lower, preferably 1250 ° C. or higher and 1350 ° C. It is preferable that it is below ℃. If the hot metal temperature is less than 1200 ° C., there is a concern about solidification and solidification of the flux and the hot metal itself due to the low temperature. In particular, considering the temperature guarantee in the subsequent desulfurization process and converter decarburization process, it is desirable to set the temperature to 1250 ° C. or higher. On the other hand, at 1500 ° C. or higher, the evaporation of flux due to high temperature cannot be ignored. That is, in order to suppress the evaporation of the sulfur-containing flux and perform the copper removal reaction efficiently, the lower the hot metal temperature is preferable, and therefore, the hot metal temperature should be 1350 ° C. or lower for efficient copper removal reaction. Is desirable.

  The carbon concentration in the hot metal before the copper removal treatment is preferably 2% by mass or more. It is known that the reaction in which the copper in the hot metal becomes copper sulfide proceeds more thermodynamically as the carbon concentration in the hot metal is higher. If the carbon concentration in the hot metal before the copper removal treatment is less than 2% by mass, the formation reaction of copper sulfide does not occur sufficiently, the liquidus temperature of the hot metal rises, and the hot metal adheres to the vessel wall. It becomes a problem. Furthermore, the copper concentration in the hot metal before the copper removal treatment is preferably 0.1% by mass or more and 1.0% by mass or less. When the copper concentration in the hot metal before the copper removal treatment exceeds 1.0% by mass, the amount of the sulfur-containing flux necessary for removing copper becomes excessive, and the practical load is large. On the other hand, when it is less than 0.1% by mass, it can be dealt with by, for example, diluting with a hot metal having a low copper content without performing a copper removal treatment.

  Furthermore, the sulfur concentration of the hot metal before the copper removal treatment is preferably 0.01% by mass or more, and more preferably 0.05% by mass or more. If the sulfur concentration of the hot metal before the copper removal treatment is less than 0.01% by mass, the amount of sulfur dissolved from the sulfur-containing flux into the hot metal becomes excessive, and the use efficiency of the sulfur-containing flux is lowered, which is not economical. The upper limit of the sulfur concentration does not need to be specified in particular, but if it is too high, the desulfurization treatment will be hindered, so it is desirable to set it to 0.5% by mass or less.

  As the hot metal components other than those described above before the copper removal treatment, for example, the silicon concentration is preferably 0.5% by mass or less and the manganese concentration is preferably 0.5% by mass or less. When these concentrations are exceeded, silicon oxide and manganese oxide generated by oxidation of these components during the copper removal treatment are transferred to slag to increase the amount of slag, making slag treatment difficult, as well as silicon oxide and manganese oxide. May inhibit the copper removal reaction of the sulfur-containing flux.

  In addition, the hot metal for steelmaking produced by carburizing and melting copper-containing steel scraps is mixed with hot metal extracted from a blast furnace (hereinafter referred to as “blast furnace hot metal”) as necessary, and then the mixed hot metal is mixed. Copper contained may be removed using a sulfur-containing flux.

  As a process for producing hot metal by carburizing and dissolving copper-containing steel scrap, there are a method using an electric furnace, a method using a converter, a method using a vertical furnace, etc. A method using a vertical furnace in which a bed is formed is preferable.

  Here, a vertical furnace with a charcoal bed formed inside is a steel containing copper-containing steel scraps and coke from the upper part of the vertical furnace and, if necessary, a slagging agent, and is provided at the lower part of the vertical furnace. The coke is burned by blowing air, oxygen-enriched air, oxygen gas, hot air, etc. from the heated tuyere, and the copper-containing steel scrap and iron making agent are melted by the combustion heat of the coke, and the hot metal is melted from the tap at the bottom of the furnace. And an apparatus for taking out molten slag. The hot metal taken out from the hot water outlet at the bottom of the furnace flows through the refractory cast iron provided in the cast floor in front of the furnace and falls into a hot metal holding container such as a hot metal pan located below the tip of the cast iron. Then, it is accommodated in the hot metal holding container. In this case, only the coke is packed in the range from the furnace bottom to a certain height above the tuyere, and this is burned to melt the copper-containing steel scrap charged in the upper part of the coke. The coke that fills the bottom of the furnace is called a “charcoal bed”, and the charcoal bed burns and wears out. To compensate for this, the coke is charged from the top of the furnace body. The molten iron produced by melting the copper-containing steel scraps flows down the coke gap and is carburized by the coke to produce hot metal. It is known that a vertical furnace having a charcoal bed formed therein has higher energy efficiency than an electric furnace or the like.

  When hot metal is produced using such a vertical furnace in which a carbon material bed is formed, the sulfur concentration in the hot metal is generally higher than that in the blast furnace hot metal. Taking advantage of this high sulfur concentration, copper removal with a sulfur-containing flux can be advantageously advanced. Since the sulfur concentration in the hot metal is high, there is little movement of sulfur from the sulfur-containing flux into the hot metal, and the utilization efficiency of the sulfur-containing flux can be increased.

  When melting copper-containing steel scraps using a vertical furnace, the hot metal taken out from the pouring spout flows through the cast iron and is dropped and injected into the hot metal holding container. The decoppering treatment can be performed by supplying the sulfur-containing flux by, for example, adding on top, blowing with the gas, or blowing with the gas. The sulfur-containing flux supplied to the hot metal flowing through the cast iron is not only decopperized during the period when the hot metal flows through the hot metal, but also vigorously stirred with the hot metal by dropping from the cast iron into the hot metal holding container. Thus, the copper removal treatment of the hot metal is efficiently performed. In this case, the copper removal reaction is further promoted by separately placing a sulfur-containing flux in the hot metal holding container in advance. In addition, when the copper removal is insufficient only by the copper removal treatment in the cast iron, the copper removal treatment can be further performed using the mechanical stirring type refining apparatus and the flux blowing method described above.

  Along with the copper removal treatment, sulfur in the sulfur-containing flux inevitably moves into the hot metal, so the sulfur concentration in the hot metal increases. Therefore, after the copper removal treatment, a treatment for removing sulfur in the hot metal is further performed. The desulfurization treatment may be any of a method using a known mechanical stirring type refining device, a method by blowing powder from a lance, a method using a converter, and the like. As the desulfurization agent, various desulfurization agents such as a desulfurization agent mainly composed of CaO, a desulfurization agent mainly composed of calcium carbide, a desulfurization agent mainly composed of soda ash, and metallic Mg can be used. After performing the copper removal treatment with the mechanical stirring type refining device, the generated slag may be removed, and then the desulfurization treatment may be performed with the same mechanical stirring type refining device. Moreover, when implementing a desulfurization process, a blast furnace hot metal may be additionally mixed with the hot metal which performed the decoppering process, and the mixed hot metal desulfurization process may be performed after that. Furthermore, you may mix a blast furnace hot metal with the hot metal after a desulfurization process.

Prior to the desulfurization treatment, it is necessary to remove the sulfur-containing flux subjected to the decopperization treatment from the reaction vessel. This is because if the desulfurization treatment is performed without removing the sulfur-containing flux, copper sulfide (Cu ₂ S) in the sulfur-containing flux is decomposed and returned to the hot metal, which may increase the copper concentration in the hot metal. The slag removal operation may be any of a method using a known slag dragger, a method using a slag suction machine, a method of discharging the slag in the container by inclining the hot metal container, and is suitable for the equipment situation possessed by each steelworks You can select the one you want.

  As described above, according to the present invention, after the copper-containing steel scrap is carburized and melted, the copper in the hot metal brought from the steel scrap is separated and removed into the sulfur-containing flux. Can be separated efficiently by the method of separating and removing by magnetic separation etc. after it is decomposed efficiently, and sulfur in the hot metal brought from the sulfur-containing flux after copper removal treatment Therefore, hot metal with less copper and sulfur can be efficiently obtained from the copper-containing steel scrap.

Using a vertical furnace with a charcoal bed formed inside, copper-containing steel scrap is melted to produce hot metal for steel making, and this hot metal is removed using a flux containing FeS-Na ₂ S as a main component. After the treatment and the copper removal treatment, a test was further carried out using a CaO-based desulfurization agent.

In the copper removal treatment, about 5 tons of the hot metal for steel making was charged into a pan-shaped reaction vessel, and in a mechanical stirring type refining device, a flux containing FeS-Na ₂ S as a main component (of Na ₂ S in the flux). Molten fraction 0.4) is put on the hot metal, the impeller coated with refractory is immersed in the hot metal, and the impeller is rotated to stir the hot metal and the flux (Test No. 1), and the reaction vessel In the case where the stirring gas is blown from the injection lance soaked in the molten iron and the flux containing FeS-Na ₂ S as a main component is added while the molten metal is stirred (Test No. 2), The test was carried out at three levels, as in the case where a flux mainly composed of FeS-Na ₂ S was blown into the hot metal and added from the injection lance immersed in the hot metal into the hot metal (Test No. 3). In any test, 200 kg of flux containing FeS—Na ₂ S as a main component was introduced per ton of hot metal.

  After the copper removal treatment, the generated slag is removed, and in each of test No.1, test No.2 and test No.3, the impeller coated with a refractory is immersed in hot metal in a mechanical stirring type refining device. The desulfurization treatment was performed by rotating and stirring the hot metal and the desulfurizing agent. Table 1 shows the transition of the copper concentration and sulfur concentration in the hot metal and the transition of the hot metal temperature.

  As shown in Table 1, in test No. 1 in which hot metal and sulfur-containing flux were stirred with an impeller in a mechanical stirring type refining device, the copper concentration in the hot metal decreased significantly from 0.33 mass to 0.10 mass%. Was. Further, in test No. 3 in which the sulfur-containing flux was blown and added, the copper concentration in the hot metal was greatly reduced from 0.30 mass to 0.11 mass%, as in test No. 1. On the other hand, in test No. 2 in which the sulfur-containing flux was added while stirring the hot metal with the stirring gas, the copper removal rate was low, but the copper removal treatment was preferably performed with a mechanical stirring type refining device. I was able to confirm.

  In Test No. 1 and Test No. 3, it was found that by performing desulfurization treatment, it was possible to finally obtain hot metal having both a low copper concentration and a low sulfur concentration, and it could be used without any problem as hot metal for high-grade steel.

  A test for performing a copper removal treatment and a desulfurization treatment after the copper removal treatment was carried out using hot metal for steel making having different temperatures and compositions (Test Nos. 4 to 13).

The copper removal treatment was performed by charging a hot metal for steelmaking in a pan-shaped reaction vessel and adding a flux for decopper refining from a refining agent supply hopper provided on the pan. As the flux for copper removal refining, 40 kg of iron-sulfur alloy (ferrosulfur, sulfur content: 48 mass%) per ton of hot metal and 30 kg of soda ash (Na ₂ CO ₃ ) per ton of hot metal were used. As a method of stirring the hot metal in the pan, a method was used in which an impeller coated with a refractory was immersed in the hot metal, and the hot metal and flux were stirred by rotating the impeller.

  In all tests, the slag produced after the copper removal treatment was removed, and after the slag was removed, the desulfurization treatment was carried out in a mechanical stirring type refining apparatus. The desulfurization treatment was performed by adding 20 kg of CaO-based desulfurizing agent per ton of molten iron, immersing the impeller coated with the refractory in the molten iron, rotating the impeller, and stirring the molten iron and the desulfurizing agent. Table 2 lists hot metal temperatures and hot metal components before and after the copper removal treatment and after the desulfurization treatment. For the hot metal components other than those shown in Table 2, the silicon concentration is 0.05 to 0.4 mass%, the manganese concentration is 0.05 to 0.4 mass%, and the phosphorus concentration is 0.02 to 0.2 mass%. It was the range of mass%.

  In Test Nos. 4 to 9, the hot metal temperature is 1200 ° C. or more and 1500 ° C. or less, the carbon concentration is 2% by mass or more, the copper concentration is 0.1% by mass or more and 1.0% by mass or less, and the sulfur concentration is 0.01%. It is within the range of the conditions of mass% or more, that is, the preferred conditions of the present invention, and the copper removal rate (= copper concentration in the hot metal after treatment / copper concentration in the hot metal before treatment) is 0.4 or more and the copper removal is good. It was confirmed that this was done. On the other hand, in Test Nos. 10 to 13, since the copper removal treatment was performed under conditions that deviated from the preferred conditions of the present invention, the copper removal rate (= (copper concentration in hot metal before treatment−copper concentration in hot metal after treatment) ) × 100 / copper concentration in hot metal before treatment) was less than 40%.

Using a vertical furnace with a charcoal bed inside, copper-containing steel scraps are melted to produce hot metal for steel making, and this hot metal is used as a starting material soda ash (Na ₂ CO ₃ ) and iron-sulfur alloy. (Ferrosulfur) is used to decopperize, and after decoppering, blast furnace hot metal is mixed with the hot metal after decoppering, and the mixed hot metal is desulfurized using a CaO-based desulfurizing agent. A test was conducted.

  The temperature of the hot metal for steel making produced in the vertical furnace was 1400 ° C., the carbon concentration was 4.0% by mass, the copper concentration was 0.30% by mass, and the sulfur concentration was 0.11% by mass.

  In the copper removal treatment, about 60 tons of hot metal for steel making is charged into a pan-shaped reaction vessel, and 35 kg of soda ash and iron-sulfur alloy (sulfur concentration in alloy is 48 mass%) per ton of hot metal in a mechanical stirring type refining device. 50 kg was put on the hot metal, the impeller covered with the refractory was immersed in the hot metal, and the impeller was rotated to stir the hot metal and the flux. The copper concentration of the hot metal after the copper removal treatment was 0.14% by mass, and the sulfur concentration was 0.44% by mass.

  After removing the slag produced by the copper removal treatment with a slag dragger, about 60 tons of hot metal after the copper removal treatment and about 240 tons of blast furnace hot metal produced in a blast furnace were mixed in a pan-shaped reaction vessel. The copper concentration in the hot metal after mixing was 0.03% by mass, and the sulfur concentration was 0.09% by mass.

  For the molten iron after mixing, in a mechanical stirring type refining device, 20 kg of CaO-based desulfurizing agent is added per ton of molten iron, the impeller covered with refractory is immersed in the molten iron, and the impeller is rotated to stir the molten iron and desulfurizing agent. Then, desulfurization treatment was performed. The copper concentration of the hot metal after the desulfurization treatment was 0.03% by mass, and the sulfur concentration was 0.01% by mass.

An investigation test was conducted to clarify the effect of hot metal temperature on the copper removal rate. About 5 tons of hot metal for steel making was charged into a pot-shaped reaction vessel, and a copper removal test was conducted (Test Nos. 14 to 20). A flux for removing copper refining was added from a hopper for supplying a refining agent provided on the pan. An iron-sulfur alloy (ferrosulfur, sulfur content: 48% by mass) and soda ash (Na ₂ CO ₃ ) were used as the flux for copper removal refining. As a method for stirring the hot metal in the pan, a method was used in which an impeller coated with a refractory was immersed in the hot metal, and the impeller was rotated and stirred. Table 3 lists the test conditions and test results. Regarding the components other than those listed in Table 3, the hot metal component before the copper removal treatment is 4.5 to 4.7% by mass of carbon, 0.20% by mass of silicon, 0.15% by mass of manganese, and 0% of phosphorus. The test was carried out with a preparation of 0.050 mass%.

  FIG. 1 shows the relationship between the hot metal temperature before the copper removal treatment and the copper removal rate. When the hot metal temperature was 1250 to 1500 ° C., the lower the hot metal temperature, the higher the copper removal rate. However, at a test level of 1200 ° C., the copper removal rate decreased to 33.3%. This is presumably because the reactivity of the decopper refining flux deteriorated due to low temperature. From this result, it was found that a high copper removal rate exceeding 50% can be obtained by setting the hot metal temperature in the range of 1250 to 1350 ° C.

  A decoppering treatment test was carried out by blowing a copper removal refining flux into the hot metal via an injection lance, with respect to about 5 tons of steelmaking hot metal accommodated in a pan-shaped reaction vessel (test No. 21 to 21). 26). In the test, an injection lance coated with a refractory was immersed in the hot metal in the pan, and a part or all of the decopper refining flux was blown into the hot metal through the injection lance using nitrogen gas as a carrier gas. In addition to the addition from the injection lance, the addition was performed from the hopper for supplying the refining agent on the pan.

An iron-sulfur alloy (ferrosulfur, sulfur content: 48 mass%) and soda ash (Na ₂ CO ₃ ) were used for the flux for copper removal refining. Table 4 shows a list of test conditions and test results. Regarding the components other than those listed in Table 4, the hot metal components before the copper removal treatment are 4.5 to 4.7% by mass of carbon, 0.20% by mass of silicon, 0.15% by mass of manganese, and 0% of phosphorus. The hot metal temperature was set to 1400 ° C.

  Regarding the immersion depth of the injection lance, if the bath depth of the hot metal is H (m) and the distance from the hot metal bath surface to the tip of the injection lance is L (m), L / H should be 0.3 or more. It has been confirmed in a separate experiment that the blown flux can contribute to the copper removal reaction. Moreover, as a specification of the injection lance to be used, any specification may be used as long as it can withstand the process of dipping in the hot metal and blowing the flux. Further, the relationship between the flow rate of the conveying gas and the flux blowing speed has no influence on the metallurgical characteristics as long as the flux clogging does not occur in the injection lance. There is no problem as long as the kind of the carrier gas is an inert gas, for example, Ar gas may be used.

  In Test Nos. 21 to 26, the ratio of addition by injection lance was changed, but there was no significant difference in the copper removal rate and it was about 50%, confirming that it was the same as when using a mechanical stirring type refining device did. In Test No. 25, only soda ash was blown and added from the injection lance, and in Test No. 26, only ferrosulfur was blown and added. All tests had the same copper removal rate. .

  From the above results, it was confirmed that the copper removal treatment was possible not only by the mechanical stirring type refining apparatus but also by a method of adding a part or all of the flux with an injection lance.

Claims (12)

  The hot metal for steelmaking is manufactured by carburizing and melting copper-containing steel scraps, and then copper contained in the hot metal is removed using a sulfur-containing flux, and then sulfur contained in the hot metal is removed. , A method for removing copper in steel scraps. The method for removing copper in steel scrap according to claim 1, wherein the sulfur-containing flux contains Na ₂ S as a main component. As starting materials of the sulfur-containing flux, the material and iron as the main component Na ₂ CO ₃ -, characterized by using sulfur alloy, the removal of copper in steel scraps according to claim 1 or claim 2 Method.   The hot metal before removing copper by the sulfur-containing flux is such that the temperature is 1200 ° C. or more and 1500 ° C. or less, the carbon concentration is 2% by mass or more, and the copper concentration is 0.1% by mass or more and 1.0% by mass or less. The method for removing copper in steel scraps according to any one of claims 1 to 3, characterized in that:   The method for removing copper in steel scraps according to claim 4, wherein the hot metal before removing copper by the sulfur-containing flux has a temperature of 1250 ° C or higher and 1350 ° C or lower.   The hot metal before removing copper by the sulfur-containing flux has a sulfur concentration of 0.01% by mass or more, in steel scraps according to any one of claims 1 to 5, Copper removal method.   The method for removing copper in steel scraps according to any one of claims 1 to 6, wherein the copper contained in the hot metal is removed by a mechanical stirring type refining apparatus.   The steel according to any one of claims 1 to 6, wherein the copper contained in the hot metal is removed by blowing a sulfur-containing flux into the hot metal in a reaction vessel together with a carrier gas. A method for removing copper from scraps.   The steel scraps according to any one of claims 1 to 8, wherein the copper-containing steel scraps are carburized and melted using a vertical furnace in which a carbonaceous bed is formed. Copper removal method.   The copper-containing steel scrap is carburized and melted using a vertical furnace having a carbonaceous bed formed therein, and the sulfur-containing flux is supplied to the hot metal flowing from the vertical furnace to the hot metal holding vessel. The method for removing copper in steel scraps according to any one of claims 1 to 6, wherein copper in the molten iron is removed.   The method for removing copper in steel scraps according to any one of claims 1 to 10, wherein the removal treatment of sulfur contained in the hot metal is performed with a mechanical stirring type refining apparatus.   The blast furnace hot metal is mixed with the hot metal after copper is removed by the sulfur-containing flux, and then sulfur contained in the hot metal mixed with the blast furnace hot metal is removed. The removal method of the copper in the steel scrap as described in one.

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